Protozoal and parasitic diseases in an animal are difficult to treat. Various medicaments have been used to treat various protozoal and parasitic diseases with limited success. The safety and effectiveness of these, medicaments depend, in large part, on the route of administration and on the type and severity of the protozoal or parasitic disease.
Babesiosis is one example of such a disease. In tropical regions, babesiosis is one of the most prevalent diseases that infects domestic animals including, but not limited to, horses, cattle and dogs. Babesia parasitize and multiply in erythrocytes. The natural defense mechanism used by the infected animal against this organism includes the destruction of infected erythrocytes by phagocytosis, particularly by macrophages, and cytotoxic lymphocytes.
The two most common species of Babesia infecting horses are Babesia caballi and Babesia equi. B. equi is the more pathogenic of these two species. Several vectors such as ticks, mosquitoes and certain varieties of sucker flies, transmit the B. equi organism from horse to horse. The clinical manifestations of babesiosis disease include fever, malaise, anorexia, anemia, jaundice and hemoglobinuria. In South American countries, it is estimated that 50% of all racing horses are infected with Babesia, which results in a decrease in racing performance.
Many medicaments have been used to treat babesiosis disease. Thus far, the best results have been achieved with the chemotherapeutic agent imidocarb 3,3'-di-2-imidazolin-2-ylcarbanilide). Imidocarb is highly effective in treating B. caballi, but only moderately effective for the treatment of B. equi. Unfortunately, the administration of midocarb causes several undesirable side effects such as excessive salivation, lacrimation, increased frequency of defecation, tachypnea and abdominal pain, leading to a colic of toxic origin. It is very important that the medicament used to treat babesiosis not only reduce the symptoms of the disease, but also eliminate the infection completely from the animal. This is necessary to prevent transmission of Babesia from an animal that, though symptomless, remains a carrier and can transmit the disease to a healthy animal.
Schistosomiasis is an example of a protozoal (platyhelminth) disease that infects animals and is a health problem of immense proportion. The disease is caused by infection with species of Schistosoma such as S. mansoni, S. japonicum and S. haematobium. This disease is characterized by symptoms including pulmonary inflammation, malaise, fever, anemia, diarrhea and abdominal pain. Most infected individuals undergo a debilitating course of chronic infections that can result in death.
Many medicaments have been used to treat schistosomiasis. Thus far, the best results have been achieved with the drug praziquantel (2-(cyclohexylcarbonyl)-1,2,3,6,7-11b-hexahydro-4H-pyrazino[2,1-a]isoquino lin-4-one]). However, as this drug does not prevent re-infection, it cannot prevent the further transmission and spread of the disease.
Trichinellosis is an example of a protozoal (nematode) disease. Trichinellosis, caused by members of the genus Trichinella, infects more than 100 species of vertebrates, including man, and has a worldwide distribution. Trichinella causes a severe inflammatory reaction in the intestine of the infected animal. This inflammatory reaction appears to result from a nonspecific immune response, which is T-cell dependent (Miller, HRP. 1984. Veterinary Immunology and Immunopathology, 6:167).
Numerous other examples of protozoal and parasitic diseases are known that have various sequelae and cause debilitating effects in infected individuals. Moreover, such diseases, because they are endemic in certain areas of the world, result in significant disruption of the social and economic development of these areas.
Therefore, what is needed is method for preventing, treating or eliminating a variety of protozoal and parasitic diseases, by administering to an animal, by a variety of administration routes, a therapeutic agent that is safe, effective, and causes minimal or no adverse side effects.